I think I am maybe being paranoid, but reading the label on the bits and the inhalation caution. Any thoughts on this running through to the end product which will most likely be inhaled/smoked?)
Plutonium for fungus gnats:
http://rinconvitova.com/predator mite.htm#Hypoaspis miles
1 jar can treat 6kwatt grow and even an infestation will be dead in 3 days tops. I love the steel wool idea as a preventive measure though may give this a try.